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NEW YORK — The Super Bowl commercial blitz is extending beyond the usual talking babies and office chimps to engage viewers online and get more for advertisers’ $3 million-plus investment.

Marketers are using every trick in the playbook to dominate the buzz before the game and long afterward, too. The gimmicks include online contests, a car “race” powered by Twitter mentions, and a secret new level of a hit iPhone game.

The goal is to build buzz, not get lost in the 42 minutes of Super Bowl ad time, and get cheap or free exposure when viewers watch again on YouTube.

“Nowadays you’ve got to get more out of your investment than 110 million viewers watching a 60-second spot,” said Steve Cannon, head of marketing for Mercedes-Benz USA.

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As part of a tie-in to the automaker’s first Super Bowl ad, which introduces five new vehicle models and celebrates the company’s 125th anniversary, Mercedes developed a pre-game race among four teams headed for the Super Bowl in Arlington, Texas. The racers’ speed is dictated by the number of tweets they receive.

Advertisers have bought up all the commercial time on Fox’s broadcast. Last year, space was still available near game time, but for this year’s contest, it was gone by October. Thirty seconds of air time is selling for $3 million, up slightly from last year’s $2.97 million, according to Kantar Media. Most other nights of the year, a 30-second prime-time commercial runs between $100,000 and $500,000.

Companies covet the Super Bowl audience because it is huge and because viewers are paying attention. As people spend more time on computers and smartphones and browse among 500 cable channels, it’s perhaps the only broadcast that allows advertisers to reach such a broad audience.

“It’s the most efficient media buy out there. Where do you pull such numbers consistently?” said Bob Horowitz, producer of the annual TV show “Super Bowl’s Greatest Commercials.” “It also delivers a huge female audience.”

The ad lineup features both familiar and new characters. Budweiser’s classic Clydesdales return, E-Trade sticks with its talking babies, and Careerbuilder.com brings back its office chimps.

Following its hit ad last year with Betty White and Abe Vigoda on a football field, Mars Inc.’s Snickers brand will reprise its theme “You’re Not You When You’re Hungry,” this time with comedians Roseanne Barr and Richard Lewis.

A musical odd couple, Justin Bieber and Ozzy Osbourne, will star in Best Buy’s first Super Bowl commercial, which is still under wraps.

Standing out in an increasingly crowded Super Bowl ad lineup takes more than a funny gag or celebrity of the moment.

“We’re seeing social media embraced by Super Bowl advertisers like never before,” said Tim Calkins, marketing professor at Northwestern University’s Kellogg School of Management. He said advertisers can get a lot of traffic for a rather modest investment by capitalizing on social media.

Among the gimmicks advertisers are using to extends their ads’ impact:

— Twentieth Century Fox will air an ad for the animated movie “Rio” that contains a code that will unlock a secret level in the popular smartphone game “Angry Birds.” The level will let users enter a sweepstakes for a trip to Rio de Janeiro on March 22 for the film premiere.

— PepsiCo’s six ads for Doritos and Pepsi Max were created by consumers and selected by popular vote at Pepsi’s www.crashthesuperbowl.com. Ten finalists got $25,000 and a trip to the game. The creators of the seven commercials have a shot at prizes of up to $1 million if the spots rank at or near the top of USA Today’s ad meter.

— Anheuser-Busch posted still images from three Bud Light ads on Facebook two weeks before the game. If people who “Like” Bud Light on Facebook correctly guess the plot of the ads, a fourth online-only ad will be unlocked.

“Before, everyone asked, ‘What was the best spot?’ But now, people are broadening their idea of what that means,” said Steve Slivka, chief creative officer of Colossal Squid Industries, a digital ad agency in Chicago.

For Mercedes, the social-media push seems to be working.

Since its Tweet race was announced, Mercedes’ Facebook following has more than tripled to 85,000 fans. It started a Twitter account for the race, which now has 73,000 followers. And since the racers began posting YouTube videos when the race started Tuesday, they have been viewed 1.8 million times.